The ability of exogenous S. mutans to implant and be retained in dental plaque varies considerably among human subjects. Because of differences in susceptibility to implantation by S. mutans, test subjects were divided into three groups: 1) Highly susceptible; 2) Moderately susceptible; and 3) Not susceptible. The purpose of the present investigation is to determine if a significant correlation exists between host saliva and S. mutans implantation by initially assessing the effects of these salivas on bacterial growth, acid production, aggregation, and ability to adhere to surfaces - all activities involved in the caries process. Results will be compared with respect to the three test groups.